In the technical field of engine control devices, there has heretofore been known a technique of adequately controlling valve opening and closing timings of each of an intake valve and an exhaust valve of an engine to thereby enhance engine operation efficiency, particularly, in a compression self-ignition combustion operating range. Further, as a means to control opening and closing of each of an intake valve and an exhaust valve of an engine, there have been known a so-called mechanical valve operating mechanism configured to open and close such an engine valve at constant intervals and in a constant lift amount, according to the shape of a cam nose provided on the surface of a cam, and a hydraulic variable valve operating mechanism configured to control a lift start timing and a lift amount, using oil pressure, without fully depending on the shape of the cam nose (e.g., the following Patent Document 1).